Germanium chemical mechanical polishing

ABSTRACT

A method of planarizing/polishing germanium is described. The method comprises the step of abrading the surface of a substrate comprising germanium with an aqueous chemical mechanical polishing (CMP) composition comprising an oxidizing agent, a particulate abrasive, and a germanium etching inhibitor. The germanium etching inhibit is selected from the group consisting of a water-soluble polymer, an amino acid having a non-acidic side chain, a bis-pyridine compound, and a combination of two or more thereof. The polymer can be a cationic or nonionic polymer that comprises basic nitrogen groups, amide groups, or a combination thereof.

FIELD OF THE INVENTION

This invention relates to chemical mechanical polishing (CMP)compositions and methods. More particularly, this invention relates to amethod for CMP removal of germanium.

BACKGROUND

Compositions and methods for CMP of the surface of a substrate are wellknown in the art. Compositions for chemical mechanicalpolishing/planarizing various substrates (also known as polishingslurries, CMP slurries, and CMP compositions), e.g., semiconductorsubstrates in integrated circuit manufacture, typically contain anabrasive, various additive compounds, and the like.

In conventional CMP techniques, a substrate carrier or polishing head ismounted on a carrier assembly and positioned in contact with a polishingpad in a CMP apparatus. The carrier assembly provides a controllablepressure to the substrate, urging the substrate against the polishingpad. The pad and carrier, with its attached substrate, are movedrelative to one another. The relative movement of the pad and substrateserves to abrade the surface of the substrate to remove a portion of thematerial from the substrate surface, thereby polishing the substrate.The polishing of the substrate surface typically is further aided by thechemical activity of the polishing composition (e.g., by oxidizingagents, acids, bases, or other additives present in the CMP composition)and/or the mechanical activity of an abrasive suspended in the polishingcomposition. Typical abrasive materials include silicon dioxide, ceriumoxide, aluminum oxide, zirconium oxide, and tin oxide.

Germanium is a useful semiconductor material in advanced metal oxidesemiconductor (MOS) transistor structures for integrated circuits (IC),e.g., in designs utilizing shallow trench isolation (STI) techniques,due to the higher electron mobility and hole mobility of germaniumrelative to silicon. Planarization of germanium under oxidativeconditions is required to prepare acceptable MOS structures undercurrent integrated circuit design parameters. Unfortunately, germaniumoxides are highly soluble, resulting in high static etching rates (SER)in the presence of oxidants such as hydrogen peroxide. The high SER, inturn leads to dishing problems when germanium is planarized using CMPcompositions comprising hydrogen peroxide or other oxidants, which canseverely limit options for advanced IC design using germanium. Cationicsurfactants have been evaluated in the past as germanium etchinginhibitors; however, such materials lead to foaming problems during CMP,which severely limits their practical usefulness.

The methods described herein address the etching and dishing problemsassociated with germanium CMP by utilizing certain germanium etchinginhibitor materials in the CMP slurries, which do not suffer from thefoaming problems of cationic surfactants and which provide suitably lowroughness surfaces for advanced germanium IC applications with minimaldishing.

SUMMARY

A method of planarizing/polishing germanium is described. The methodcomprises the step of abrading the surface of a substrate comprisinggermanium with an aqueous CMP composition comprising an oxidizing agent(e.g., about 0.5 to about 4 percent by weight (wt %) hydrogen peroxide),a particulate abrasive such as colloidal silica (e.g., at aconcentration in the range of about 0.1 to about 5 wt %, preferablyabout 0.5 to about 3 wt %), and a germanium etching inhibitor. Thegermanium etching inhibitor is selected from the group consisting of awater-soluble polymer, an amino acid having a non-acidic side chain, abis-pyridine compound, and a combination of two or more thereof.

The water-soluble polymer can be a cationic or nonionic polymer thatcomprises basic nitrogen groups, amide groups, or a combination thereof.These groups can be substituents situated along the polymer backbone(e.g., a hydrocarbon, ester, amide, or ether backbone), can form part ofthe polymer backbone (e.g., as in some polyimides), or both. In someembodiments, the polymer comprises basic nitrogen groups selected fromprimary amino groups, secondary amino groups, tertiary amino groups,quaternary amino groups, and a combination of two or more thereof,and/or basic nitrogen heterocyclic groups, such as pyridine, imidazole,or quaternized versions thereof. In some other embodiments, the polymercomprises amide groups selected from the group consisting of —C(═O)NH₂,—C(═O)NHR, —C(═O)NR₂, and a combination of two or more thereof,typically as substituents on a hydrocarbon (e.g.,“polyvinyl”or“polyolefin”) backbone, e.g., polyacrylamide compounds,wherein each R independently is a hydrocarbon moiety (e.g., lower alkyl,such as methyl, ethyl, propyl, etc.). In yet other embodiments, thepolymer can comprise amide groups and basic nitrogen groups.

Polyacrylamide-type nonionic polymers bearing —C(═O)NH₂ and/or —C(═O)NHRamide groups are preferred non-ionic polymers for use in thecompositions and methods described herein. Non-limiting examples of suchmaterials include; polyacrylamide (PAM), poly(N-isopropylacrylamide)(PNIPAM), PAM copolymers, and the like.

Useful cationic polymers include one or more polymers selected from thegroup consisting of a poly(diallyldimethylammonium)halide such aspoly(diallyldimethylammonium)chloride (polyDADMAC), apoly(methacryloyloxyethyltrimethylammonium)halide such aspoly(methacryloyloxyethyltrimethylammonium)chloride (polyMADQUAT),poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine) (polyDEE), andthe like. In some embodiments, the cationic polymer can comprise bothamide groups and basic nitrogen groups, e.g., as in a copolymer ofacrylamide (AAm) and DADMAC, such as polyAAm-co-DADMAC. In somepreferred embodiments, the polymer is present in the CMP composition ata concentration in the range of about 10 to about 2000 parts-per-million(ppm).

The amino acid-based germanium etching inhibitors are amino acids thathave non-acidic side chain. In some cases, the amino acids preferablyhave a basic side chain, a hydrophobic side chain, and/or have anisoelectric point of 6 or greater. Non-limiting examples of such aminoacids include lysine, arginine, histidine, glycine, beta-alanine,valine, and N-(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)glycine) also knownas tricine. Preferably, the amino acid is present in the composition ata concentration in the range of about 50 to about 5000 ppm.

Bis-pyridine-type Ge etching inhibitors are compounds comprising twopyridine groups linked together via a covalent bond (i.e., bipyridylcompounds) or through a 1 to 3 carbon linking group. In someembodiments, the Ge etching inhibitor comprises at least one compoundselected from the group consisting of 4,4′-trimethylenedipyridine,1.2-bis(4-pyridyl)ethane, 2,2′-bipyridyl, and1,2-bis(2-pyridyl)ethylene. Preferably, the bis-pyridine compound, ifutilized, is present in the composition at a concentration in the rangeof about 50 to about 5000 ppm.

In one embodiment, the particulate abrasive, e.g., colloidal silica, ispresent in the CMP composition at a concentration in the range of about0.5 to about 3 wt %, and the polymer is present at a concentration ofabout 10 to about 1000 ppm. In other embodiments, the CMP compositioncomprises about 0.5 to about 3 wt % of the abrasive (e.g., colloidalsilica, and about 50 to about 5000 ppm of the amino acid. In yet otherembodiments, the CMP composition comprises about 0.5 to about 3 wt % ofthe abrasive (e.g., colloidal silica), about 10 to about 1000 ppm of thepolymer, and about 50 to about 5000 ppm of the amino acid.

The methods described herein are suitable for planarizing Ge andSi_(x)Ge_((1-x)) (for x=about 0.1 to about 0.9) materials and providesurprisingly good germanium removal rates without significant dishingdue to germanium etching and low surface roughness, without creatingfoaming problems during the CMP process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a graph comparing the Ge static etch rate (SER) observedfor CMP compositions containing various polymer-type Ge etchinginhibitor compounds.

FIG. 2 provides graphs of Ge SER, as well as removal rates for Ge andsilicon oxide (Ox), and selectivity for Ge/Ox observed for CMPcompositions comprising various concentrations of polyMADQUAT (ALCO4773).

FIG. 3 provides a graph comparing the Ge static etch rate (SER) observedfor CMP compositions containing various amino acid and pyridine Geetching inhibitor compounds.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The CMP compositions useful in the methods described herein include anoxidant (e.g., hydrogen peroxide), a particulate abrasive (e.g.,colloidal silica and the like), and a germanium etching inhibitor (e.g.,a water soluble nonionic polymer, a water-soluble cationic polymer, andamino acid, a bis-pyridine compound, or a combination of two or morethereof) in an aqueous carrier.

Oxidizing agents useful in compositions and methods described hereininclude, e.g., hydrogen peroxide, ammonium persulfate, potassiumpermanganate, and the like. Hydrogen peroxide is the preferred oxidizingagent. Preferably, the oxidizing agent, e.g. hydrogen peroxide, ispresent in the composition at a concentration in the range of about 0.1to about 4 wt %, more preferably about 0.5 to about 3.5 wt %), at thepoint of use (i.e., diluted for use in the polishing process).

The term “water-soluble” as used herein, refers to polymers thatdissolve in water, or are dispersible in water, to form substantiallyclear, transparent dispersions. The water-soluble polymer can be acationic or nonionic polymer that comprises basic nitrogen groups, midegroups, or a combination thereof. In some embodiments, the polymercomprises basic nitrogen groups selected from primary amino groups,secondary amino groups, tertiary amino groups, quaternary amino groups,and a combination of two or more thereof, and/or basic nitrogenheterocyclic groups, such as pyridine, imidazole, or quaternizedversions thereof. In some other embodiments, the polymer comprises amidegroups selected from the group consisting of —C(═O)NH₂, —C(═O)NHR,—C(═O)NR₂, and a combination of two or more thereof, typically assubstituents on a hydrocarbon (e.g., “polyvinyl” or “polyolefin”)backbone, e.g., polyacrylamide compounds, wherein each R independentlyis as hydrocarbon moiety (e.g., lower alkyl, such as methyl, ethyl,propyl, etc.). In yet other embodiments, the polymer can comprisecarbonamide groups and basic nitrogen groups.

Polyacrylamide-type nonionic polymers bearing —C(═O)NH₂ and/or —C(═O)NHRamide groups are preferred non-ionic water-soluble polymers for use inthe compositions and methods described herein. Non-limiting examples ofsuch materials include, polyacrylamide (PAM),poly(N-isopropylacrylamide) (PNIPAM, PAM copolymers, and the like.

Cationic polymers useful as germanium etching inhibitors in thecompositions and methods described herein include homopolymers ofcationic monomers, e.g., a poly(diallyldimethylammonium)halide such aspoly(diallyldimethylammonium)chloride (polyDADMAC), apoly(methacryloyloxyethyltrimethylammonium)halide such aspoly(methacryloyloxyethyltrimethylammonium)chloride (polyMADQUAT), andthe like. In addition, the cationic polymer can be a copolymer ofcationic and nonionic monomers (e.g., alkylacrylates,alkylmethacrylates, acrylamide, styrene, and the like), such aspoly(acrylamide-co-diallyldimethylammonium)chloride (polyAAm-DADMAC),and poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine) (polyDEE).Some other non-limiting examples of such cationic polymer includepolyethyleneimine, ethoxylated polyethyleneimine,poly(diallyldimethylammonium)halide, poly(amidoamine),poly(methacryloyloxyethyldimethylammonium)chloride,poly(vinylpyrrolidone), poly(vinylimidazole), poly(vinylpyridine), andpoly)vinylamine). A preferred cationic polymer for use in the CMPcompositions of the invention is apoly(methacryloyloxyethyltrimethylammonium)halide (e.g., the chloride),also known as polyMADQUAT, such as ALCO 4773, which is commerciallyavailable from Alco Chemical Inc.

Alternatively, or in addition, the cationic polymer can includenitrogen-heteroaryl or quaternized nitrogen-heteroaryl groups, i.e.,heteroaromatic compounds comprising at least one nitrogen in an aromaticring, optionally having at least one of the nitrogen atoms in the ringalkylated to impart a formal positive charge on the heteroaryl ring(e.g., on a nitrogen in the ring). Preferably, the heteroaryl group isattached to the backbone of the polymer through a carbon-carbon bond(e.g., as in a quaternized poly(vinylpyridine)polymer) or acarbon-nitrogen bond (e.g., as in a quaternizedpoly(vinylimidazole)polymer) either directly to the aromatic ring orthrough an alkylene spacer group (e.g., methylene (CH₂) or ethylene(CH₂CH₂) group). The positive charge on the quatenized nitrogen isbalanced by a counter anion, which can be, e.g., a halide (e.g.,chloride), nitrate, methylsulfate, or any combination of anions. In someembodiments, the cationic polymer comprises, consists essentially of, orconsists of a poly(vinyl-N-alkylpyridinium)polymer, such as apoly(2-vinyl-N-alkylpyridinium)polymer, apoly(4-vinyl-N-alkylpyridinium)polymer, a vinyl-N-arkylpyridiniumcopolymer, a poly(N1-vinyl-N3-alkylimidazolium)polymer, and the like.

The polymer preferably is present in the CMP composition at aconcentration of about 10 to about 2000 ppm (more preferably bout 10 toabout 1000), at point of use in a polishing method as described herein.

The molecular weight of the polymer is not limited, but typically, thepolymer has a weight average molecular weight of about 5 kDa or more(e.g., about 10 kDa or more, about 20 kDa or more, about 30 kDa or more,about 40 kDa or more, about 50 kDa or more, or about 60 kDa or more)cationic polymer. The polishing composition preferably comprises apolymer having a molecular weight of about 100 kDa or less (e.g., about80 kDa or less, about 70 kDa or less, about 60 kDa or less, or about 50kDa or less). Preferably, the polishing composition comprises a polymerhaving a molecular weight of about 5 kDa to about 100 kDa (e.g., about10 kDa to about 80 kDa, about 10 kDa to about 70 kDa, or about 15 kDa toabout 70 kDa.

Amino acids useful as germanium etching inhibitors in the compositionsand methods described herein include amino acids that have non-acidicside chains. In some preferred embodiments, the amino acid comprises abasic side chain, such as e.g., lysine, arginine, and histidine. Inother embodiments, the amino acid has a hydrophobic side chain (e.g.,alanine, leucine, isoleucine, valine, phenylglycine). In yet otherembodiments, the amino acid is selected from amino acids having anisoelectric point of 6 or greater (e.g., lysine, arginine, histidine,glycine, beta-alanine, valine, and the like). Preferably, the amino aciddoes not include a sulfur-containing side chain (e.g., methionine,cysteine, or cystine). Examples of some preferred amino acids include,e.g., lysine, arginine, histidine, glycine, beta-alanine, tricine, andvaline. Preferably, the amino acid is present in the composition at aconcentration in the range of about 50 to about 5000 ppm.

Bis-pyridine-type Ge etching inhibitors are compounds comprising twopyridine groups linked together via a covalent bond (i.e., bipyridylcompounds) or through a 1 to 3 carbon linking group, e.g., compounds ofthe formula Pyr-R′-Pyr, in which Pyr is a pyridine group, which can besubstituted (e.g., with an alkyl group) or unsubstituted. Each Pyrindependently is attached to R′ at the 2, 3, or 4 position of thepyridine ring. R′ can be a covalent bond (in which case the compoundsare bipyridyl compounds), (CH₂)n, or CH═CH, wherein n is 1, 2, or 3.When R′ is CH═CH, the Pyr groups can be attached to CH═CH in the E or Zorientation. Non-limiting examples of bis-pyridine-type Ge etchinginhibitors include, e.g., 4,4′-trimethylenedipyridine,1,2-bis(4-pyridyl)ethane, 2,2′-bipyridyl, 1,2-bis(2-pyridyl)ethylene,and the like. Preferably, the bis-pyridine compound, if utilized, ispresent in the composition at a concentration in the range of about 50to about 5000 ppm.

The particulate abrasive can comprise any abrasive material suitable foruse in CMP of semiconductor and integrated circuit materials. Examplesof such materials include, e.g., silica, ceria, zirconia, and titania. Apreferred particulate abrasive is silica (e.g., colloidal silica).Preferably, the particulate abrasive has a mean particle size of about20 to about 200 nm. Preferred colloidal silica has a mean particle sizeof about 60 to about 150 nm (e.g., about 120 nm). Preferably, theabrasive (e.g., colloidal silica) is present in the CMP composition at aconcentration of about 0.2 to about 3 wt % (e.g., about 0.4 to about 2wt %), at point of use. The colloidal silica particles can have anyshape. In some embodiments the colloidal silica particles are generallyspherical, cocoon-shaped, or a combination thereof. Optionally, thecolloidal silica can include additional cationic materials (e.g.,quaternary amines) on the surface of the silica particles to impart apositive zeta potential to the surface.

The CMP compositions of the present invention can have any pH, butpreferably have a pH in the range of about 1.5 to about 9 (e.g., about 2to about 5). The pH of the composition can be achieved and/or maintainedby inclusion of a buffering material, as is well known to those ofordinary skill in the chemical arts.

The polishing compositions of the invention optionally also can includesuitable amounts of one or more other additive materials commonlyincluded in polishing compositions, such as metal complexing agents,dispersants, corrosion inhibitors, viscosity modifying agents, biocides,inorganic salts, and the like. For example, the composition can includea biocide such as KATHON, KORDEK, or NEOLONE biocides; a complexingagent such as acetic acid, picolinic acid, tartaric acid, iminodiaceticacid, benzoic acid, nitrilotriacetic acid (NTA), and the like; and/or acorrosion inhibitor such as benzotriazole (BTA), 1,2,3-triazole,1,2,4-traizole, a tetrazole, 5-aminotetrazole, 3-amino-1,2,4-triazole,phenylphosphonic acid, methylphosphonic acid; and the like.

The aqueous carrier can be any aqueous solvent, e.g., water, aqueousmethanol, aqueous ethanol, a combination thereof, and the like.Preferably, the aqueous carrier comprises predominately deionized water.

The polishing compositions used in the methods described herein can beprepared by any suitable technique, many of which are known to thoseskilled in the art. The polishing composition can be prepared in a batchor continuous process. Generally, the polishing composition can beprepared by combining the components thereof in any order. The term“component” as used herein includes individual ingredients (e.g.,abrasive, polymer, amino acid, buffers, and the like), as well as anycombination of ingredients. For example, the abrasive can be dispersedin water, combined with the etching inhibitor components, and mixed byany method that is capable of incorporating the components into thepolishing composition. Typically, the oxidizing agent is not added tothe polishing composition until the composition is ready for use in aCMP process. For example, the oxidizing agent can be added just prior toinitiation of polishing. The pH can be further adjusted at any suitabletime by addition of an acid, base, or buffer, as needed.

The polishing compositions of the present invention also can be providedas a concentrate, which is intended to be diluted with an appropriateamount of aqueous solvent (e.g., water) prior to use. In such anembodiment, the polishing composition concentrate can include thevarious components dispersed or dissolved in aqueous solvent in amountssuch that, upon dilution of the concentrate with an appropriate amountof aqueous solvent, each component of the polishing composition will bepresent in the polishing composition in an amount within the appropriaterange for use.

The compositions and methods of the invention surprisingly provide lowsurface roughness and significant reductions in SER (e.g., 80% orgreater reductions in SER) compared to similar CMP slurry formulationsthat do not contain the etching inhibitor materials.

The CMP methods of the invention preferably are achieved using achemical-mechanical polishing apparatus. Typically, the CMP apparatuscomprises a platen, which, when in use, is in motion and has a velocitythat results from orbital, linear, and/or circular motion, a polishingpad in contact with the platen and moving relative to the platen when inmotion, and a carrier that holds a substrate to be polished bycontacting and moving relative to the surface of the polishing pad. Thepolishing of the substrate takes place by the substrate being placed incontact with the polishing pad and a polishing composition of theinvention and then moving the polishing pad relative to the substrate,so as to abrade at least a portion of the substrate to polish thesubstrate.

The following examples further illustrate certain aspects of theinvention but, of course, should not be construed as in any way limitingits scope. As used herein and in the following examples and claims,concentrations reported as parts-per-million (ppm) or percent by weight(wt %) are based on the weight of the active component of interestdivided by the weight of the composition, and are on a point of usebasis.

EXAMPLE 1

This example illustrates the effect of selected cationic and nonionicpolymers on Ge SER and removal rates.

Ge blanket wafers with (100) preferred orientation were planarized withaqueous CMP slurries (at a pH of about 2.3) comprising about 2 wt %colloidal silica, 2 wt % hydrogen peroxide, and various polymeradditives at a concentration of 100 ppm. The Ge removal rates (RR) andstatic etch rates (SER) were evaluated. Planarization was accomplishedon a POLI 500 brand polisher using an IC1010 brand polishing pad at aplaten speed of about 60 rpm, a carder speed of about 63 rpm, a downforce of about 1.5 psi, and a slurry flow rate of about 100 mL/minute;polishing time: 60 seconds. SER was determined by dipping the wafers in35 ° C. and 45° C. slurries with oxidizer present, for two minutes.

In one evaluation, the effects of various polymers on Ge SER wasdetermined. The characteristics of the slurries are described in Table 1along with SER values, and the SER results are provided in FIG. 1,reported as normalized SER as a percentage of the SER obtained with aslurry that did not include any polymer additive. The normalized SER wasset at 100% for the composition that did not contain any etchinginhibitor component.

TABLE 1 Slurry SER (Å/min) Polymer 1 105 polyMADQUAT (ALCO 4773) 2 206polyDEE (PDEE) 3 223 polyDADMAC (PDADMAC) 4 271 polyAAm-DADMAC(PAAM-DADMAC) 5 137 PAM

As is evident from FIG. 1, the polymers all provided surprisingreductions in Ge SER in the range of about 84 to 94%.

In another evaluation, Ge removal rates and SER were evaluated forslurries comprising 2 wt % of commercially available colloidal silica(cocoon-shaped particles, primary particle size of about 30 to 35 nm,secondary particle size of about 70 nm, cationic surface-modified), 2 wt% hydrogen peroxide, and 0 to 1000 ppm of polyMADQUAT. In addition, theslurries were evaluated for PETEOS silicon oxide removal rates, and forthe selectivity of Ge:Ox (Ge removal versus silicon oxide removal).Planarization was accomplished, on a POLI 500 brand polisher using anIC1010 brand polishing pad at a platen speed of about 60 rpm, a carrierspeed of about 63 rpm, a down force of about 1.5 psi, and a slurry flowrate of about 100 mL/minute; polishing time: 60 seconds. SER wasdetermined, by dipping the wafers in 35° C. and 45° C. slurries withoxidizer present, for two minutes. The results are shown in FIG. 2.

The results in FIG. 2 indicate that the effects of the polyMADQUATleveled off after about 100 ppm polymer concentration, and that therewas a significant selectivity for Ge removal versus oxide removal of >12at polymer concentrations in the range of 100 to 1000 ppm.

EXAMPLE 2

This example illustrates the effects of various amino acids and apyridine compound on Ge SER.

Ge blanket waters with (100) preferred orientation were planarized withCMP slurries comprising 2 wt % commercially available colloidal silica(cocoon-shaped particles, primary particle size of about 30 to 35 nm,secondary particle size of about 70 nm, cationic surface-modified), 2 wt% hydrogen peroxide, and various amino acid and pyridine additives,i.e., 1000 ppm of lysine, D,L-methionine, arginine, histidine, and4,4′-trimethylenedipyridine; and 100 ppm of glycine, beta-alanine,valine, aspartic acid, glutamic acid, phenylalanine, andN-(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)glycine (also known astricine). Planarization was accomplished on a POLI 500 brand polisherusing an IC1010 brand polishing pad at a platen speed of about 60 rpm, acarrier speed of about 63 rpm, a down force of about 1.5 psi, and aslurry flow rate of about 100 mL/minute; polishing time: 60 seconds. SERwas determined by dipping the wafers in 35° C. and 45° C. slurries withoxidizer present, for two minutes. The SER results are provided in FIG.3, reported as normalized SER as a percentage of the SER obtained usinga slurry without any polymer additive.

The data in FIG. 3 clearly indicate that the pyridine compound and aminoacids with non-acidic side chains provided significant Ge SERreductions. Acidic amino acids such as aspartic acid and glutamic acidwere ineffective, while methionine and phenylglycine provided somesuppression of SER, but were significantly less effective than the othernon-acidic amino acids. Lysine, arginine, histidine, glycine,beta-alanine, and valine all reportedly have an isoelectric point, pI,of 6 or greater, whereas methionine, phenylglycine the acidic aminoacids have a pI of less than 6_(—) Consequently, in some embodiments,the preferred amino acid-type Ge etching inhibitors have an isoelectricpoint of 6 or greater.

EXAMPLE 3

This example illustrates the effects of lysine, arginine and polyMADQUATon Ge removal (RR) and Ge SER.

Ge blanket wafers with (100) preferred orientation were planarized withaqueous CMP slurries (at a pH of about 2.3) comprising colloidal silica,hydrogen peroxide, and various combinations of polyMADQUAT (ALCO 4773),lysine and arginine. The Ge removal rates (RR) and static etch rates(SER) were evaluated. Planarization was accomplished on a POLI 500 brandpolisher using an IC1010 brand polishing pad at a platen speed of about60 rpm, a carrier speed of about 63 rpm, a down force of about 1.5 psi,and a slurry flow rate of about 100 mL/minute; polishing time: 60seconds. SER was determined by dipping the wafers in 35° C. and 45° C.slurries with oxidizer present, for two minutes. Table 2 provides asummary of the colloidal silica materials used and silicaconcentrations, the amino acids and concentration thereof, the polymerconcentration, and the hydrogen peroxide concentration, as well as theobserved, germanium SER and RR. Preferred target SER and RR are <100Å/min and 200-2000 Å/min, respectively.

TABLE 2 Silica SER Sam- Wt % Amino acid, Alco4773 H₂O₂ (Å/min) Ge RR ple(PS*) (Conc. ppm) (Conc. ppm) Wt % @35° C. (Å/min) A 2% (30) 0 0 2.0%~1500 ~2250 B 2% (30) 0 100 2.0% ~150 ~400 C 2% (30) 0 325 2.0% 291 149D 2% (30) 0 1000 2.0% 154 139 E 2% (50) Lys (1000) 0 2.0% 270.4 849.7 F2% (50) Lys (5000) 0 2.0% 199.3 745.1 G 2% (50) Arg (1000) 0 2.0% 207.11847.2 H 2% (50) Arg (5000) 0 2.0% 261.3 2120.1 I 2% (50) Lys (5000) 3252.0% 94 260 J 1% (50) Arg (1000) 10 2.0% 102 1555 K 1% (50) Arg (1000)10 1.0% 99 1633 L 1% (50) Arg (1000) 10 0.5% 14 1196 M 1% (50) Arg(1000) 25 2.0% 103.9 671.3 N 1% (50) Arg (1000) 50 2.0% 97.9 493.7 O 1%(50) Arg (5000) 10 2.0% 87.0 1231.5 P 1% (50) Arg (5000) 50 2.0% 85.7529.7 *PS = nominal primary particle size of cationic surface-modifiedcolloidal silica, in nm

As is evident from the data in Table 2, the combinations of amino acidplus polyMADQUAT generally provided SER values within or very close tothe preferred range of <100 Å/min while also maintaining the Ge removalrates within the desire target range of 200 to 2000 Å/min.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The terms “consisting of” and“consists of” are to be construed as closed terms, which limit anycompositions or methods to the specified components or steps,respectively, that are listed in a given claim or portion of thespecification. In addition, and because of its open nature, the term“comprising” broadly encompasses compositions and methods that “consistessentially of” or “consist of” specified components or steps, inaddition to compositions and methods that include other components orsteps beyond those listed in the given claim or portion of thespecification. Recitation of ranges of values herein are merely intendedto serve as a shorthand method of referring individually to eachseparate value falling within the range, unless otherwise indicatedherein, and each separate value is incorporated, into the specificationas if it were individually recited herein. All numerical values obtainedby measurement (e.g., weight, concentration, physical dimensions,removal rates, flow rates, and the like) are not to be construed asabsolutely precise numbers, and should be considered to encompass valueswithin the known limits of the measurement techniques commonly used inthe art, regardless of whether or not the term “about” is explicitlystated. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate certain aspects of the invention and does not pose alimitation on the scope of the invention unless otherwise claimed. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including,the best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A method of polishing germanium comprising the step of abrading the surface of a substrate comprising germanium with an aqueous chemical mechanical polishing (CMP) composition comprising an oxidizing agent, a particulate abrasive, and a germanium etching inhibitor comprising a cationic polymer selected from the group consisting of poly(diallyldimethylammonium)chloride (polyDADMAC), poly(methacryloyloxyethyltrimethylammonium)chloride (polyMADQUAT), poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine) (polyDEE), and a copolymer of acrylamide and DADMAC, plus an amino acid selected from the group consisting of lysine, arginine, histidine, glycine, beta-alanine, tricine, and valine. 2.-10. (canceled)
 11. A method of polishing germanium comprising the step of abrading the surface of a substrate comprising germanium with an aqueous chemical mechanical polishing (CMP) composition comprising an oxidizing agent, a particulate abrasive, and a germanium etching inhibitor comprising a bis-pyridine compound of formula Pyr-R′-Pyr, wherein each Pyr independently is a pyridine group attached to R′ at the 2, 3, or 4 position of the pyridine group; R′ is a covalent bond, (CH₂)n, or CH═CH; and n is 1, 2, or
 3. 12. The method of claim 11 wherein the bis-pyridine compound comprises at least one compound selected from the group consisting of 4,4′-trimethylenedipyridine, 1,2-bis(4-pyridyl)ethane, 2,2′-bipyridyl, and 1,2-bis(2-pyridyl)ethylene.
 13. The method of claim 1 wherein the amino acid is present in the composition at a concentration in the range of about 50 to about 5000 parts-per-million (ppm).
 14. The method of claim 1 wherein the water-soluble polymer is present in the CMP composition at a concentration in the range of about 10 to about 2000 ppm.
 15. The method of claim 1 wherein the bis-pyridine compound is present in the composition at a concentration in the range of about 50 to about 5000 ppm.
 16. The method of claim 1 wherein the particulate abrasive comprises colloidal silica at a concentration in the range of about 0.5 to about 3.5 percent by weight (wt %).
 17. The method of claim 1 wherein the CMP composition comprises about 0.5 to about 3.5 wt % of the colloidal silica, and about 10 to about 2000 ppm of the water soluble polymer.
 18. The method of claim 1 wherein the CMP composition comprises about 0.5 to about 3.5 wt % of the colloidal silica, and about 50 to about 5000 ppm of the amino acid.
 19. The method of claim 1 wherein the CMP composition comprises about 0.5 to about 3.5 wt % of the colloidal silica, about 10 to about 2000 ppm of the polymer, and about 50 to about 5000 ppm of the amino acid.
 20. The method of claim 1 wherein the oxidizing agent comprises hydrogen peroxide at a concentration in the range of about 0.5 to about 4 wt %. 